From: Benjamin Gray <bgray@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Benjamin Gray <bgray@linux.ibm.com>
Subject: [PATCH 2/3] powerpc/watchpoint: Disable pagefaults when getting user instruction
Date: Tue, 29 Aug 2023 16:34:56 +1000 [thread overview]
Message-ID: <20230829063457.54157-3-bgray@linux.ibm.com> (raw)
In-Reply-To: <20230829063457.54157-1-bgray@linux.ibm.com>
This is called in an atomic context, so is not allowed to sleep if a
user page needs to be faulted in and has nowhere it can be deferred to.
The pagefault_disabled() function is documented as preventing user
access methods from sleeping.
In practice the page will be mapped in nearly always because we are
reading the instruction that just triggered the watchpoint trap.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
arch/powerpc/kernel/hw_breakpoint_constraints.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/hw_breakpoint_constraints.c b/arch/powerpc/kernel/hw_breakpoint_constraints.c
index a74623025f3a..9e51801c4915 100644
--- a/arch/powerpc/kernel/hw_breakpoint_constraints.c
+++ b/arch/powerpc/kernel/hw_breakpoint_constraints.c
@@ -131,8 +131,13 @@ void wp_get_instr_detail(struct pt_regs *regs, ppc_inst_t *instr,
int *type, int *size, unsigned long *ea)
{
struct instruction_op op;
+ int err;
- if (__get_user_instr(*instr, (void __user *)regs->nip))
+ pagefault_disable();
+ err = __get_user_instr(*instr, (void __user *)regs->nip);
+ pagefault_enable();
+
+ if (err)
return;
analyse_instr(&op, regs, *instr);
--
2.41.0
next prev parent reply other threads:[~2023-08-29 6:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-29 6:34 [PATCH 0/3] Fix preemption errors in watchpoints Benjamin Gray
2023-08-29 6:34 ` [PATCH 1/3] powerpc/watchpoints: Disable preemption in thread_change_pc() Benjamin Gray
2023-08-29 6:34 ` Benjamin Gray [this message]
2023-08-29 6:34 ` [PATCH 3/3] powerpc/watchpoints: Annotate atomic context in more places Benjamin Gray
2023-08-29 6:42 ` [PATCH 0/3] Fix preemption errors in watchpoints Benjamin Gray
2023-09-21 9:24 ` Michael Ellerman
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